Modelling of Ignition Process for Premixed Combustion in a Constant Volume Bomb

Abstract

Computational Fluid Dynamics is a widespread tool employed in the design of Internal Combustion Engines (ICE), mainly focused to improve efficiency and reduce pollutant emissions. Given the complexity associated with solving turbulent, multiphase, chemically reacting flows, many models have been proposed to represent as accurate as possible phenomena taking place inside ICE, keeping computational costs below reasonable levels. Specifically, mixture ignition and initial flame kernel development are decisive factors affecting the whole combustion process in spark-ignition engines, and current ignition models are not able to correctly predict the flame behavior when ICE operative conditions are varied, making it a subject that has drawn attention over the last years. In the present work, an ignition model taken from the literature named ISSIM (Imposed Stretch Spark Ignition Model), originally developed for LES (Large Eddy Simulation) is implemented in OpenFOAM(R) and adapted here to work with eddy viscosity models using RANS (Reynolds-Average Navier-Stokes) equations. Ignitions of air-propane mixtures in a constant volume bomb are simulated for different equivalence ratios and turbulent intensity levels, analyzing the dependence of the solution on the electrical parameters of the spark-ignition system. Results are contrasted with experimental data selected from the literature, and furthermore, advantages and drawbacks are discussed compared to other ignition models used in common practice.